The present invention relates to a magnetic recording medium and a method of producing the same and, more specifically, it relates to a thin film type magnetic recording medium used for a hard disk drive and a method of producing the same, capable of improving a CSS (contact start and stop) property and a sticking property of the magnetic head to the surface of the magnetic recording medium, and simultaneously capable of lowering a flying height of the magnetic head.
Usually, information is written into and read out of a recording medium by means of a magnetic head, in which the disk is rotated at a high speed to hover the magnetic head. In the disk, texturing for applying a mechanical polishing is applied to make texturing traces (texture pattern) on the surface of the disk concentrically in the circumferential direction of the disk (hereinafter referred to as mechanical texture) for improving a magnetic characteristic. Generally, the mechanical texture is applied on the surface of the non-magnetic substrate or on an under layer such as an Ni-P layer plated thereon.
Since a recent increasing of data amount and demand for miniaturizing and the light weighting the device, the linear recording density and track density are increased, so that scratches caused by the existent mechanical texture result in a reading or writing error at a high probability.
Accordingly, it has been proposed a method of applying the mechanical texture only in a CSS zone at the inner circumference of the disk while leaving a data recording zone as it is. However, the surface of the data recording zone is made higher than the height for the surface of the CSS zone, to bring about a problem that the magnetic head crushes upon seeking.
Further, a method of making the texture pattern by a laser beam (hereinafter referred to as laser texture)has also been proposed instead of the mechanical texture. For instance, in U.S. Pat. specifications Nos. 5,062,021 and 5,108,781, there is proposed an attempt of locally melting a Ni-P layer by a Q-switch laser beam of Nd-YAG, in which a pulse width is very narrow and an energy density is very high, and forming crater-like projections, thereby improving the CSS property with respect to the magnetic head by the circular rim of the protrusions.
However, by the texture pattern produced by the laser texture disclosed in above-mentioned patents, the area of contact with respect to a lower surface of the magnetic head is not decreased outstandingly, and it can not be deemed that the problem of sticking between the magnetic head and the disk is improved more compared with the mentioned using mechanical texture.
Further, a method of forming projections by using photolithography has also been proposed. For instance, preprint for Tribology published by The Japan Society of Tribologists (1991-5, A-11), (1992-10, B-6) show the result of CSS test for disks having concentric projections formed by photolithography at a 0.1 to 5% area ratio relative to the entire surface of the disk.
However, since the top of the projection formed by in the above-mentioned method is flat, it involves a drawback that the frictional force is increased along with the sliding cycles of the magnetic head and that industrial application is not easy.